1Any of various games played with a ball by swimmers in water; specifically a team game resembling water polo.
2A game in which two teams propel a ball with jets of water from powerful hoses, (in later use) especially (chiefly US) one in which each team attempts to propel a ball suspended from an overhead cable over a line defended by the opposing team.
Chiefly with reference to games played by firefighters at fêtes, fairs, or similar events.
3US A toy or ornament in the form of a transparent globe or dome that encloses a liquid in which particles or bubbles move, typically around a model of a scene, when it is shaken.
4A large, transparent, inflatable PVC ball which can be propelled across water by a person inside running or walking, usually as an entertainment or leisure activity.
Mid 17th century (in an earlier sense). From water + ball.